bridge location

fatdaddypreacher

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been searching on best way to mathmaticaly locate bridge on new construction. LP style build. Normally I install the tailpiece, nut, and tuners and install both e strings, sliding the bridge in place til i reach good intonation (with saddles centered), but can't do that on this build as readily, as this is going out as a kit, less hardware. I saw somewhere the numbers that show how to adjust the angle of bridge, but for the life of me can't find it anywhere. Don't know what happened ti all the stickied build threads either. thanks.
 

Wallied

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This post by Jack Briggs is one that explains one way to do it by measuring.

Cheers, Will
 

fatdaddypreacher

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This post by Jack Briggs is one that explains one way to do it by measuring.

Cheers, Will
thanks. i'll check that out. you would think one could trust jack:)
 

fatdaddypreacher

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so, if i interpret this correctly, he adds 2mm to the treble side towards the tailpc, and 5mm on the base, thus establishing a difference of 3mm slant to the tailpc. i assume adding the 2mm to the treble is to center the saddle to the desired distance from the 12th fret. i'm sure i can screw this up pretty easilly.
 

fatdaddypreacher

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i've never done one strictly by doing the math, so this makes me a little nervous, especially since i won't have it available in the event it needs a little adjustment to the hole location. would be easy enough to dowel and redrill, but dlon't have that option. thanks.
 

Roxy13

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Can you put a trapeze TP on and set the bridge on something? I have this large assortment of grommets and used those under the bridge to get the string height I like. Then strung it up and intonated the bridge. When I was certain it was exactly where it should be then I drilled the holes.

And my degree is in, uh, mathematics.
 

fatdaddypreacher

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that's normally exactly what i do. it's just a little awkward without having tuners in place. the tuners he's using is different than what i have, so i can't dummy something up like i normally would. thx
 

Spotcheck Billy

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This is what LtDave32 says:
"
Measure from the face of the nut to the center point of the 12th fret. Transfer that same measurement from the center point of the 12th fret to the lower bout, marking a straight line across the body with a pencil (perpendicular to the centerline).

Lay a ruler against each side of the neck, down the body, and mark two lines that are perpendicular to the first line you drew.

Between those neck lines, where they intersect the first line, measure up from the treble side 1/16" BELOW the original line. Make a mark at that measurement.

Again between the neck lines, on the bass side of the body, mark a spot on the bass side 5/32" BELOW the original line.

Draw the angled line between these two points.

This is your bridge line.

On wrap-tail bridges, don't forget this:

1) Measure the diameter of the tailpiece stud, and cut that measurement in half. Add that half-measurement to the angled, final bridge line. This is where the drill point goes.

2) Because of the angle, the strings will flop over to the treble side of their holes. this will cause the strings to not lay dead-center over the pup pole pieces. Simply shift the final positioning of drilling the studs to the bass side 1/16" (for both studs). This will result in the strings being perfectly aligned over the pole pieces."


*Mod edit for correction.
 
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nuance97

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This is what LtDave32 says:
"
Measure from the face of the nut to the center point of the 12th fret. Transfer that same measurement from the center point of the 12th fret to the lower bout, marking a straight line across the body with a pencil (perpendicular to the centerline).

Lay a ruler against each side of the neck, down the body, and mark two lines that are perpendicular to the first line you drew.

Between those neck lines, where they intersect the first line, measure up from the treble side 1/16"BELOW the original line. Make a mark at that measurement.

Again between the neck lines, on the bass side of the body, mark a spot on the bass side 5/32" BELOW the original line.

Draw the angled line between these two points.

This is your bridge line.

On wrap-tail bridges, don't forget this:

1) Measure the diameter of the tailpiece stud, and cut that measurement in half. Add that half-measurement to the angled, final bridge line. This is where the drill point goes.

2) Because of the angle, the strings will flop over to the treble side of their holes. this will cause the strings to not lay dead-center over the pup pole pieces. Simply shift the final positioning of drilling the studs to the bass side 1/16" (for both studs). This will result in the strings being perfectly aligned over the pole pieces."
That all sounds about right EXCEPT you seem to be saying that the treble side should be behind your Nut to 12th fret distance?? That isn’t right...both the treble and bass side of the bridge have to be compensated. They should be forward of the line on the treble side 1/16” (or 1.6mm) and 5/32” (or 4mm) in the bass side.

*Those measurements are +\- .030” or so depending on string gauge or action preferences

*Mod Note* Edited for correcton.
 
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jkes01

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that's normally exactly what i do. it's just a little awkward without having tuners in place. the tuners he's using is different than what i have, so i can't dummy something up like i normally would. thx
Personally, I wouldn’t set the bridge with out being able to string it up to pitch. I couldn’t trust measurements for anything except general placement.

How different are they? You may have to source tuners like his or have him send you the ones he wants to use.
 

fatdaddypreacher

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he's over seas and pulled the trigger on the order before i could suggest he have it shipped to me. I think i might have a solution to use some tuners i didn't realize i had. that's precisely the way i feel. thanks.
 

pshupe

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That all sounds about right EXCEPT you seem to be saying that the treble side should be behind your Nut to 12th fret distance?? That isn’t right...both the treble and bass side of the bridge have to be compensated. They should be forward of the line on the treble side 1/16” (or 1.6mm) and 5/32” (or 4mm) in the bass side.

*Those measurements are +\- .030” or so depending on string gauge or action preferences


I'd like to show this graphically because that is the way I understand it. I would like to work this out as I am cutting some CNC bodies soon and if I can add this to the CNC job list that would save me considerable time. So as I have read above, this is what I have come up with.

full fret board - (ridiculous image size?? see below)
Capture.JPG



blow up of bridge location-
Capture2.JPG


Is this correct?

Regards Peter.

PS - what is going on with the images on this forum lately?? The text on both these images should be the same size. I cannot enlarge the images and if I try the re-size properties it only re-sizes in one direction. Someone should look into this as it is extremely frustrating!!!!
 
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nuance97

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I'd like to show this graphically because that is the way I understand it. I would like to work this out as I am cutting some CNC bodies soon and if I can add this to the CNC job list that would save me considerable time. So as I have read above, this is what I have come up with.

full fret board - (ridiculous image size?? see below)
View attachment 461691


blow up of bridge location-
View attachment 461686

Is this correct?

Regards Peter.

PS - what is going on with the images on this forum lately?? The text on both these images should be the same size. I cannot enlarge the images and if I try the re-size properties it only re-sizes in one direction. Someone should look into this as it is extremely frustrating!!!!
Looks good to me
 

DoneOne

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Is this correct?

yes. I believe LtDave corrected at least one of the places he posted this method, but apparently not all (or this was copied before the correction) Both the 1/16th and 5/32nds should be on the long side of the relative scale line = further from the nut.

the stewmac recommendations are pretty much in line with the authorized tech method LtDave described.

https://www.stewmac.com/FretCalculator.html - enter *relatve scale then see recommendations below after calculation. (relative scale for a rule of 18 - 24.75 board would be 24.57)

the Lt Dave method puts the bridge center 7/64ths longer than the relative scale length... stewmac's min (bass side 1/8th longer) recommendation puts the center 8/64ths longer... but going on the longer side of their + / - 0.030 marks leaves more adjustment. Remember the high E string length won't be shorter than the relative scale. so one could put that saddle near the forward allowable adjustment. The low E 1/8th back is conservative. With you kids (heh) going for lower tunings with monstrous strings, the more better extra adjustment room on the bass side.

I mention the centers because I eventually draw a circle centered on that mark to make sure the post holes are exactly the required distance apart. i.e. - bridge holes 2.9" apart on center - draw a 2.9" diameter (1.45R) circle.

9/64ths behind the relative scale is where Erlewine likes it... which suggests he uses the +0.030 side of the sm recommendation.


how could gibson be that far off on their bridge placement in 1964? I've already harped on the nut to first fret measurement being inconsistent in production... and the error being doubled when determining relative scale... so I'll save myself the typing
 
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ARandall

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^ You wonder if there was a 'new machinery setup' taking place, and somehow in the process an addition was done instead of a subtraction (or vise versa)......compounded by the '1st-12th and double it'.
 

DoneOne

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^ You wonder if there was a 'new machinery setup' taking place, and somehow in the process an addition was done instead of a subtraction (or vise versa)......compounded by the '1st-12th and double it'.

it's a mystery... 59 bursts a bit shorter... juniors a bit longer. Not knowing the specific process they went through, it's hard to say if it was mis- placement in the gang saw or whether they were trimmed (or not) later. It's surprising because the mgt usually set the processes to avoid screwups - to be self correcting. i.e. bridge not being placed until the neck was set in case the angle of the neck was a bit off when it was fitted. Neck a bit crooked in relation to the body center line? - doesn't matter because the neck center line becomes the center line for the bridge and pup routes - done after the neck was set.

edit to add - maybe someone like preeb who has taken the kalamazoo tour might have some insight.
 

ARandall

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Oh wow, Hadn't realised that different guitar models had different 'results'.
 

DoneOne

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I should clarify that I've only seen accurate measurements of all frets for a few vintage guitars. The bursts measured by preeb and bartlett and 2 juniors measured by FreddyG.... so concluding that it depends on the model isn't necessarily valid. It may be that the bursts got more attention from more experienced shop hands than juniors.. but you'd think an es335 would get experienced hands on it. It may be that they varied on all models - depending on who or when they were done.

as stated previously, it's a mystery. All I know is that the gang saw was reasonably accurate on the few measurements I've seen and that the error lies between the nut and first fret.
 

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